This is a direct piggyback off the Stock/Finance/Econometric Resources thread...
DS7 is down the "money" rabbit trail in a big way right now. It's not just our money, it's really about currency as a whole. I know "currency" hasn't always been money and has been around since the beginning of time, but has anyone seen an "evolution of currency" or "history/evolution of financial systems" or even a comparison of varying financial systems used worldwide that would be accessible at this age? (This age defined as 5th grade reading level or below). We've visited local mints and even colonial mint museums, but he's looking for something deeper than "this is what money looks like".
Note: a video set would be even better than a book as the depth of learning would not be limited to eye motor skills.